Two-stage hydraulic pressure pump



jam. WW 8. BEAMAN ET AL. 2, 5

TWO-STAGE HYDRAULIC PRESSURE PUMP Filed June 8, 194-5 4 Sheets-Sheet 1 ax W B. BEAMAN ET AL, 2,495,,5

TWO-STAGE HYDRAULIC PRESSURE PUMP Filed June 8, 19 55 4 Sheets-Sheet 2 Z, 5 jg k E k I R A-m, P U P 7% fl 5 M 34} 52 1% "t Z!- s I .7 1 1 7? i 10a .13! 42 1M I Jj 14 ///1ia 5 5 m P. W

A W n 720 m TWO-STAGE HYDRAULIC PRESSURE PUMP ANNIE Filed June 8, 1945 er M Jam, M, W50 B BEAMAN ET AL 2,495,685

TWO-STAGE HYDRAULIC PRESSURE PUMP Filed June 8, 1945 4 Sheets-Sheet 4 jkrerzfari ,Bezvze rd J2 21 165 Hal/flail,

Patented Jan. 31, 1950 STATES PATENT OFFICE Bernard Beaman, .llulius Holman, and Robert A. Stein, Dayton, Ohio Application June 8, i945, Serial No. 598,356

ll'l Claims. (El. l03-5) (Gted under the act oi March 3, 1883, as amended April 3t), 1928; 370 Q. G. 757) The invention described herein may be manuiactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

Our present invention relates to a hydraulic pressure pump of two-stage character which is designed for emcient operation at extremely high pressures in-the second stage.

One object of the invention is to provide a twostage pump which is compact, the design being simple and involving but few parts which can be readily fabricated and assembled.

Another object is to provide a pump wherein loaded bearings are minimized, the thrust forces being taken by stationary thrust surfaces.

Still another object is to provide a pump wherein effective seals against fluid loss may be provided in a simple manner.

Still another object is to provide a first-stage pump of sliding vane type and a second-stage pump comprising a rotating barrel having cylinder bores therein with pistons provided in the bores and slidable by a cam.

A further object is to iloatingly mount the barrel so that it will effectively seat against an end plate of the pump under the force of internal pressure acting on partially closed cylinder bore ends, and to provide a relief valve for such pressure to maintain it at a desired value somewhat lower than the pressure in the high pressure side of the pump without exceeding such desired pressure.

Still a further object is to provide a two-stage pump wherein the mechanism of two pumps in series is built into one housing to form a compact, self-contained unit.

An additional object is to provide a high pressure piston pump which is pressurized by a low pressure vane pump, the vane pump overfeedlng the piston pump and having a pressure relief means from the outlet of the vane pump to the inlet thereof to thus maintain a predetermined charging pressure for the piston pump and to force the pistons therein against a cam without the necessity of providing return springs, linkage or some other mechanical means for this purpose.

A further additional object is to provide a structure which can be rotated in one direction for pumping liquid, an arrangement being provided for reversing the vane pump within the 2 housing in the event that it is desirable to reverse the direction of rotation of the pump shalt.

Still a further additional object is to provide a pump structure wherein an increased pressure thrust of a cylinder barrel against a valve plate is secured by reducing the unseating pressure force on the area between the barrel cylinder openings and the barrel land area. such con= struction involving a valve port diameter less than the cylinder circle diameter and permitting of multiple drilled passageways from the ends of the cylinders to the valve ports so that the flow area can be made the desired value and the drilled passageways being at an angle, thus producing an elliptical intersection between the drilled passageways and the valve ports.

With these and other objects in view, our invention consists in the construction, arrangement and combination of the various parts of our pump structure whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in our claims and illustrated in the accompanying drawings, wherein:

Fig. 1 is a front elevation of our pump;

Fig. 2 is a rear elevation thereof;

Fig. 3 is a vertical sectional view on the line 3-3 of Fig. 2;

Fig. 4 is a horizontal sectional view on the lln lll of Fig. 3;

Fig. 5 is a sectional view on the line 55 of Fig. 4 showing the pistons in the cylinder bores of the high pressure pump;

Fig. 6 is a sectional view on the line t--t of Fig. 4 showing a portion of the porting arrangement;

Fig. 7 is a-sectional view of the line l-l of Fig. 6 showing further details of the porting arrangement;

Fig. 8 is a sectional view on the line t-t of Fig. 4 showing the low pressure pump;

Fig. 9 is a sectional view on the line Sl-t of Fig. 4 showing a reversing arrangement for the low pressure pump;

Fig. 10 is an end view of a portion of Fig. 9 looking in the direction of the arrow It adjacent thereto;

Fig. 11 is a sectional view on the line i l-ll of Fig. 9 showing further details thereof;

Fig. 12 is a sectional view on the line l2l2 of Fig. 5 showing a pressure relief valve for the low pressure pump;

enemas Fig. 13 is a sectional view on the line I8-I8 of Fig. 12;

Fig. 14 is a front view of the pressure relief valve shown in Figs. 12 and 13, with the end plate of the housing left OH to show the relationship of parts;

Fig. 15 is a sectional view of'a modified construction wherein an arrangement of parts is provided for increasing pressure thrust of the barrel against the end plate of the pump; and

Fig. 16 is a sectional view on the line I6I8 of Fig. 15 showing the elliptical ends of drilled passageways of the construction shown in Fig. 15.

On the accompanying drawings we have used the reference numeral I8 to indicate a cylindrical housing. The housing has a flange I2 at one of its ends for mounting the pump on an engine or the like. For this purpose, bolts or screws may extend through perforations I l of the flange and thread into the engine or any suitable support, in the usual manner. The housing I8 has a flange I8 at its other end to which an end plate I8 is secured, as by cap screws 28, with a suitable gasket or sealing compound between the flange and the end plate.

The housing I8 has an internal partition 22 against which a back plate 23 is positioned. A cam 28 is afiixed thereto as by seven large screws 28 and three small screws 21. The cam fits the interior of the housing I8 and is retained against rotation by a pair of dowels I8 and 2| which will be more fully described later on in the specification. The cam 28 has a cam face 28 which is in the form of a truncated cylinder end, and a hardened creep plate 30 of washer-like character is engaged against this face.

Rotatable in bearing surfaces 32 and 88 in the end plate I8 and the cam 28, respectively, is a barrel drive shaft 36. Loosely splined at 82 on the barrel drive shaft 86 is a barrel 84 having an annular shoulder 88 engaging the shaft 36 for guide purposes. The barrel M has a flat sealing face 58 to contact with a flat sealing face 52 of the end plate I8. The loose splining of the barrel M to the shaft 36 permits ready conformity of the face 88 to the face 52.

Circumferentially spaced cylinder bores 88 are provided in the barrel M, and in each a plungerlike piston 88 is reciprocable. Each cylinder has a cylinder port 58 of the shape shown in Fig. 5. The ports are of somewhat less cross-sectional area than the area of the cylinder bore in order to provide the necessary thrust force between the barrel M and the end plate I8 by internal pressure acting on the cylinder bore ends surrounding the ports 58. The cylinders 54 and the pistons 58 constitute a high pressure pump. The barrel 88 is adapted to be seated against the end plate I8 by pressure within the housing I8, as will hereinafter appear. During starting of the pump, when pressure has not yet built up, it is desirable to make sure that the faces 58 and 52 are in contact, and this may be accomplished by a light spring 58, as shown in Figs. 4 and 5.

A low pressure pump is provided in the form of a rotor 38 having slots 48 in which vanes 48 are slidably mounted, as shown in Fig. 8. The rotor 38 is within a stator bore 68 of the cam 24, which stator bore is eccentric with relation to the rotor to thereby effect inward and outward movement of the vanes 48.

A low pressure inlet boss 82 is provided on the end plate I8, as shown in Figs. 2 and 4. This boss communicates with a passageway 84 in the end plate which, in turn, communicates with an intake passageway 88 in the housing I8. The pa sageway 88, as shown in Fig. 4 communicat with the interior of the dowel 2| through oper lugs 88 therein, and the interior of the dowel con municates with an intake port 18 formed in ti back plate 28. This port feeds liquid into the ir take side of the low pressure pump (the left sic in Fig. 8).

An outlet port I2 is provided on the high pres sure side of the low pressure pump, and this out let communicates through openings M in th dowel I8 with an outlet passageway I6 (see Fii a). The passageway 18 extends to the inner fac 82 of the end plate I8 and communicates with O-shaped passageway 18 formed in the end 0 the housing i8 adjacent the plate I8, as show: in Fig. 5. The ends of the C-shaped passagewa. I8 communicate with a pair of passageways I which are best shown in Figs. 6 and 7, for con ducting the liquid back toward the center of rota tion into an arcuate intake port 82 formed in thi end plate I8. The passageways 88 are also former in this end plate, as clearly shown in Fig. 7.

The arcuate intake port 82 is provided for th high pressure pump, and the cylinder ports 8i thereof successively register with the port 82 an: a similar arcuate outlet port 88 which communicates directly with an outlet or high pressure bos: 86 on the end plate I8. The boss 86 is the outlet and the boss 82 is the intake, and, accordingly, there is low pressure in the boss 62 and higi pressure in the boss 86, as indicated by the legend: HI" and L0 in Figs. 2 and 4.

The dowel I8 is threaded in position and car accordingly be removed. The dowel 2| is alsi removable, it normally being retained in positior by a ring-like plug 88 which, in turn, is threaded into the housing I8. The ring-like plug has 1 hexagonal socket for convenience in removing it The dowel 2i has a lug 98 received in a notch 9% of the back plate 23. The outer end of the dowe' 2i has an arrow 94 thereon to indicate the direction of rotation for the pump.

The housing I8 has a pair of keyways 96 and 8| to selectively receive the lug 98, and the back plate 23 has a second notch I88, similar to the notch 92. It also has a serrated circumference indicated at I82'for reversing purposes as will hereinafter appear.

The rotor 88 is formed on a shaft I88 which rotates in a bearing surface I86 of the back plate 23 as shown in Figs. 4 and 5. It is connected to the barrel drive shaft 36 by a loosely splined connection I88 and with a drive shaft II8 by means 55 of a loosely splined connection H2. The drive shaft II8 has a splined end lid for connection to a power take-oil? shaft of an aircraft engine or any other suitable means to drive the pump. Such means would align the outer end of the drive shai t 60 I I8 for proper operation without binding.

The drive shaft II8 has a flange IIG surrounding it, with which a seal plate I I8, in the form of a ring, is engageable. A spring I28 effects such engagement initially, whereas fluid pressure with- 65 in the housing effects the engagement after the pump is in operation, as will hereinafter appear.

The spring I28 is seated against a second end plate I22 secured to the partition 22 by suitable 70 means such as screws I24.

The seal plate I housing I8 by means of a diaphragm I26 having its inner edge clamped to the seal plate by a spanner nut I28 and its outer edge clamped 76 between a washer I38 and the end plate I22 I8 is sealed relative to the by screws iii. This provides a pressure cham- I ber, indicated at ltii, inside of the flange lit.

The inner end of the drive shaft lit is seated against a shoulder ltd of the rotor shaft iflil which serves merely as a thrust connection, but, normally, when the pump is operating, the two are spaced from each other. it. passageway tilt is provided through the center of the rotor shaft and communicates with a passageway its through the center of the barrel shaft through which liquid is adapted to how after passing through the splined connections iii and ltd. A relief groove Milli is provided for such flow in the event that the inner end of the drive shaft tilt is seated against the shoulder it i.

The passageway communicates with a pressure relief valve in the form of a valve plug i 32 seated against a ring Hit by a spring lit. The valve plug acts as a piston in a sleeve lit which serves to guide its sliding movement. The sleeve iii; has a head its for screwing the sleeve into the end plate it at a screw-threaded connection The sleeve lit has ports ltd communicating with an annular groove its which,

turn, communicates by means of a passageway Hill with the low pressure boss (52.

The low pressure pump comprising the rotor and the vanes id is of higher capacity than the high pressure pump comprising the cylinders lit and the pistons ht. This is for the purpose of assuring full charging of the high pressure cylinders for reducing voids in the liquid and for keeping the pistons in contact with the creep plate til. To avoid excessive build-up of pres sure and to keep a substantially even charging pressure from the low pressure pump to the high pressure pump, a relief valve from the outlet of the low pressure pump to its inlet is provided. This is shown in Figs. l2, l3 and 1d and consists of a sleeve itt in a bore iti between the intake passageway iii for the low pressure pump and the high pressure passageway it. The position of this bore is best shown in Fig. 5. Referring to Fig. 13, it will be noted that there is a pair of annular grooves W3 and tilt surrounding the sleeve ltd, and passageways ltd and till serve to communicate these grooves with the passageways tit and it, respectively.

Within the sleeve ltli is a difierential pressure plunger having a large portion iii and a small portion it' l so that the liquid under high pressure from the low pressure pump acts on the bottom of the plunger portion iii! to raise it against the action of a spring lit. The spring is retained in position by a retainer ring lit, and the entire relief valve assembly is held in position by the end plate it when it is installed. The operation of this valve will be referred to hereinafter.

in Figs. 15 and 16 we have shown a modified construction wherein the cylinder barrel it, in

stead of having ports drilled axially with respect to the cylinders, has a pair of ports 58 drilled at an angle relative thereto and thus terminating in elliptical port openings 56, as shown in Fig. 16, closer to the center of rotation than the axes of the cylinders M. This provides increased pressure thrust of the barrel against the valve plate as it reduces the unseating pressure force on the area between the bar-rel cylinder openings and the barrel land area. This is basically produced by reducing the radii of the ports til and M in the end or valve plate it, their diameter thus being less than the cylinder circle diameter. Fig. clearly shows the ports i}? 58 drilled at an angle, and any number may be used (two are shown by way of illustration) per cylinder, as required to provide the desired flow passage. The barrel is preferably provided with a pair of circular lands at and it, the land t l being in alignment with the cylinder circle diameter and acting as a stabilizing land. The land it for the ports it, t2 and lit, it will be noted, is brought inside the cylinder circle diameter.

Practical operation The shaft lid is driven by any suitable power means to thereby drive the rotor shaft mil and the barrel shaft 3t. The rotor it and the bar'- rel til are thereby driven, and rotation of the rotor causes liquid to be drawn in from the intake boss 62 through the passageways t l, t6, t8 and iii to the low pressure pump. The liquid therein is pumped out through the passageways it, it, it, it, til and 82 to the pistons 56 on their inward strokes while their cylinder ports 5t communicatewith the end port d2.

Rotation around the other half of the circle causes the pistons to be forced outwardly in the cylinders 5t for forcing the oil into the high pressure outlet passageway M and the outlet boss tii. The liquid is thus pumped at low pressure by the vane pump and at high pressure by the piston pump which is charged by the low pressure vane pump, and the pressure in the outlet 86 may be relatively high, such as 3,000 pounds per square inch in the particular design of pump illustrated.

Since the vane pump overfeeds the piston pump, the relief valve, as shown in Fig. 13, will be opened by the liquid pressure overcoming the pressure of the spring i it and thereby permitting the oil from the annular passageway N56 to enter the annular passageway ltd, and find its way back to the intake side of the low pressure pump. Thus, a substantially even pressure of oil from the low pressure pump to the high pressure pump is maintained with assurance of full charging of the high pressure pump even after the pump becomes worn to some extent.

During operation the spring 59 keeps the barrel to in engagement with the end plate it, and the spring Ht keeps the seal plate H8 in engagement with the flange i it so that there is a sealed chamber within the housing It all the way from the end plate iii to the diaphragm I26. These springs, particularly the spring 59, maintain the seal necessary for priming the pump. There is some leakage of liquid past the faces 50 and E52, especially before pressure is built up in the housing ill, and this liquid, together with the small amount which creeps past the pistons 56, and any which may leak from the low pressure pump, will charge the interior of the housing It for lubricating the bearing surfaces 32, 3t and IE6, and producing pressure within the housing. The barrel it will be seated against the end plate it under the action of the charging pressure for the housing plus the internal pressure of the cylinder bores acting on the partially closed cylinder ends. The housing pressure also acts on the flange so to compress the spring I26 somewhat and thereafter maintain the flange lit against the sealing face of the seal plate i it under such pressure. The pressure is limited, however, by the relief valve M2, depending upon the strength of the spring 6. The liquid pressure will move the relief valve to a relief position, permitting the excess liquid to flow through the ports I50, I56 and I58 back to the low pressure enemas boss 62. A selected spring Mt may be used as required to keep a desired pressure within the housing. The valve M2 therefore acts as a pressure regulating valve.

Our two-stage pump can be readily adjusted for a reversal in the direction of rotation in the following described manner: The dowel it is unscrewed, and the plug 88 is unscrewed and the dowel 2! then pulled out. A screwdriver may now be inserted into the opening for the dowel 2i and engaged with the serrated periphery Hit of the back plate 23 for rotating the back plate a half turn. The housing H3 is cut away, as indicated at 99 in Fig. 9, to permit passage of the screwdriver for starting the rotation.

After the back plate has been rotated a half turn the notch it!!! will occupy a position shown by dotted lines and indicated as iilila. The dowel 21 may now be reinserted but will have to be turned over a half turn so that the lug ti] will pass through the groove 98 and enter the notch It") at the position iilila. This turns the arrow M (Fig. to a position pointing up instead of down in order to indicate that the pump is now to rotate in the opposite direction. The plug 88 can be reinserted, the dowel i9 reinserted, and the stator bore 60 will be eccentric above the rotor in Fig. 8 instead of below it. Thereupon, rotation of the pump is necessarily clockwise in Fig. 8 instead of counter-clockwise. The end plate iii may remain in the same position.

From the foregoing specification we believe it will be obvious that we have provided a structure which compactly includes both a low pressure pump and a high pressure pump, whereby a complete hydraulic pump suitable for high pressure operation is had.

The design is such that there are few parts, and they are simple to form, machine and assemble. The necessary thrust of the rotating barrel to effect pressure seal is had without the necessity of providing the spring 59 other than for the purpose of the initial thrust before pres sure is built up within the housing. The spring can therefore be comparatively light, yet will insure proper priming of the pump. The seal at il6l it! remains effective even if the shaft lift is out of alignment or eccentric, or if the splines i 08 and I l 2 should happen to stick.

The barrel M is fully floating on the barrel shaft so that it can properly seat against the end plate i8 without any binding whatever. The vanes in the low pressure pump are forced outwardly by centrifugal force, and the volume of liquid trapped between two adjacent blades alternately increases and decreases as the rotor turns, thereby giving the desired pumping action.

The inlet and outlet ports HI and 12 are preferably overlapped slightly at their lower ends with respect to adjacent vanes ii! to insure good filling of the low pressure pump, especially at high rotative speeds. The high pressure pump is preferably provided with a considerable number of pistons which is desirable to reduce pressure pulsations, and the high pressure pump is pressurized by the low pressure pump to eliminate cavitation in the high pressure pump. The low pressure pump also eliminates the necessity of springs or linkage normally used for returning the pistons of the high pressure pump.

The vane pump ports 10 and 12, it will be noted, are axial to avoid pressure drop experienced with ports of the radial entry type. All of the pumping power transmitted to the rotating barrel is carried through concentric shafts which are not subjected to any appreciable thrust. The pump is extremely compact, yet the parts are designed rugged enough for containing the high pressures generated.

With respect to the modified form shown in Figs. 15 and 16, increased pressure thrust of the barrel M against the end plate It! is had by reducing the unseating pressure forces at the parting line between these two elements. This is accomplished by reducing the circle diameter of the ports 58', 82 and ti t in the novel manner disclosed. This also has the added advantage of reducing the circle diameter of the ports 82 and 8t and permitting the use of multiple passages 68 which are slightly increased in area at the ends thereof where they match the ports 82 and at by being drilled at a slant so as to be elliptical rather than truly round in cross-section at their terminal ends at the land M Some changes may be made in the construction and arrangement of the parts of our pump without departing from the real spirit and purpose of our invention, and it is our intention to cover by our claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

We claim as our invention:

1. In a two-stage hydraulic pressure pump, a housing, a barrel drive shaft journaled therein, a barrel loosely mounted on said shaft and operatively connected thereto, said barrel having cylindrical bores therethrough substantially parallel to the axis of rotation of the barrel, a piston in each of sad bores, said barrel having one of its ends seated against an end of said housing, cylinder ports in said end of said barrel and communicating with said cylindr cal bores, a cam in said housing having a cam surface in the shape of a truncated cylinder end, said pistons cooperating with sad cam to effect sliding movement of the pistons in one direction upon rotation of said barrel, a low pressure vane pump rotor operatively connected with said barrel driving shaft and located within said cam, said cam being built to provide a stator chamber therefor, said end of said housing having intake and discharge ports, and a passageway system leading from said intake port to said low pressure pump and from said low pressure pump to an intake port in said housing end for said cylinder ports. and an outlet port in said housing communicating with said discharge ports.

2. In a two-stage hydraulic pressure pump, a housing, a barrel journaled therein and having cylindrical bores therethrough substantially parallel to the axis of rotation of the barrel, a piston in each of said bores, said barrel having one of its ends seated against an end of said housing, cylinder ports in said end of said barrel and communicating with said cylindrical bores, a cam in said housing having a cam surface in the shape of a truncated cylinder end, sad pistons cooperatng with said cam to effect sliding movement of the pistons in one direction upon rotation of said barrel, a low pressure vane pump having a rotor connected with said barrel for rotation therewith, said end of said housing having intake and discharge ports, a passageway system leading from said intake port to said low pressure pump and from said low pressure pump to an intake port in said housing end for said cylinder ports, an outlet port in said housing end for said cylinder ports, and an outlet connection from said outlet port to said discharge port.

3. In a two-stage hydraulic pressure pump, a

housing, a barrel drive shaft journaled therein, a barrel mounted thereon, said barrel having cylindrical bores therethrough, a piston in each of said bores, said barrel having one of its ends seated against an end of said housing, cylinder ports in said end of said barrel and communicating with said cylindrical bores, a cam in said housing having a truncated cylinder end, said pistons cooperating with said cam end to effect sliding movement of the pistons in one direction upon rotation of said barrel, a low pressure pump operatively connected with said barrel driving shaft and located within said housing, said end of housing having intake and discharge ports, and a passageway system leading from said intalre port to said low pressure pump, from said low pressure pump to an intake port in said housin end for said cylinder ports, and from outlet port in said housing end for said cylinde ports to said discharge port.

. a two-stage hydraulic pressure pump, a cylindrical housing, a barrel drive shaft journaled therein, barrel on said shaft and having cylindrical bores therethrough substantially parallel the axis of rotation oi the barrel, a piston in each of said bores, said barrel having one of its ends seated against an end of said housing, cylinder ports in said end of said barrel and communicating with said cylindrical bores, a cam in said housing having a cam surface in the shape of a truncated cylinder end, said pistons cooperating with said cylinder end to effect sliding movement of the pistons in one direction upon rotation of said barrel, a low pressure vane pump operatively connected with said barrel driving shaft and located within said housing in end to end relation with said barrel and cam, said end at said housing having intake and discharge ports, and a passageway system leading along one side of said housing from said intake port to said low pressure pump, along the other side of said housing from said low pressure pump to an intake port in said housing end for said cylinder ports, and from an outlet port in said housing end ior said cylinder ports to said discharge port. 5. In a hydraulic pressure pump, a housing, a barrel. drive shaft journaled therein, a barrel on said shaft and operatively connected thereto for rotation therewith, said barrel having cylindrical bores, pistons in said bores, a cam for sliding said pistons in one direction, an end plate for said housing, said barrel having one or its ends seated thereagainst, cylinder ports in said end of said barrel, said end plate having a pump inlet and a pump outlet, a low pressure pump in said' housing, said barrel and cylinders being located between said low pressure pump and said end plate, a passageway arrangement from said inlet through said housing to said low pressure pump, from said low pressure pump through said housing to said cylinder ports and from said cylinder ports to said outlet, and said passageway arrangement including dowels and a back plate having ports for said low pressure pump, said bac: plate being adjustable through 180 for permitting reversal of the rotation of said piston type and low pressure pumps and being rotatable when said dowels are removed, said dowels preventing rotation of said back plate when they are inserted in said housing, one of said dowels being coactible with said back plate in only a predetermined manner depending on the position of the back plate, and having a direction indicating element thereon to indicate the direction l of rotation depending upon the adjustment of the back plate.

6. In a hydraulic pressure pump, a housing, a barrel drive shaft journaled therein, a barrel mounted on said shaft, said barrel having cylindrical bores, pistons in said bores, a cam for sliding said pistons in one direction, an end plate for said housing, said barrel having one of its ends seated thereagainst, cylinder ports in said end of said barrel, said end plate having a pump inlet and a pump outlet, 9. low pressure pump in said housing, a passageway arrangement from said inlet to said low pressure pump, from said low pressure pump to said cylinder ports and from said cylinder ports to said out let, said low pressure pump having a baclr plate which is adjustable through 180 for permitting reversal of the rotation of said piston type and low pressure pumps, and said passageway arrangement including hollow dowels for coaction with back plate to prevent rotation thereof when they are inserted in said housing.

7. In a hydraulic pressure pump a housing, a barrel mounted for rotation therein, said barrel having cylindrical bores, pistons in said bores, a cam for sliding said pistons in one direction, said barrel having one of its ends seated against an end of said housing, cylinder ports in said end of said housing, said housing having a pump inlet and a pump outlet, a low pressure pump in said housing, and a passageway arrangement from said inlet to said low pressure pump, from said low pressure pump to said cylinder ports and from said cylinder ports to said outlet, said low pressure pump including a plate adjustable through 180 for permitting reversal of the rotation of said piston type and low pressure pumps, said plate having ports for said low pressure pump.

8. In a hydraulic pressure pump, a ho, a barrel drive shaft journaled therein, a barrel loosely mounted on said shaft and operatively connected thereto for rotation therewith, said barrel having cylindrical bores, pistons in said bores, a cam for sliding said pistons in on direc tion, an end plate for said housing, said barrel having one of its ends seated thereagainst under pressure within the housing, cylinder ports in said end of said barrel, said end plate having a pump inlet and a pump outlet, a low pressure pump in said housing including a stator chamber formed in said cam, said barrel and cylinders being located between said stator and said end plate, a passageway arrangement from said inlet through said housing to said low pressure pump, from said low pressure pump to said cylinder ports and from said cylinder ports to said outlet, said low pressure pump naving a ported back plate adjustable through 180 for permitting reto verse] of the rotation of said piston type and low pressure pumps, and said passageway arrangement including hollow dowels, said back plate being rotatable when said dowels are removed, and said dowels extending into said back plate and permitting rotation thereof when the dowels are inserted in said housing, one of said dowels being coactible with said back plate in only one predetermined manner when the back plate is in one position and in another predetermined manner when the back plate is in its other position to indicate the direction of rotation for the pump.

9. In a two-stage hydraulic pressure pump, a housing, an end plate therefor, a barrel, mounted for rotation, in said housing, a, cam, a low pressure pump and a back plate arranged in series in said housing, said barrel having a plurality of reciprocable pistons, said barrel, cam and pistons constituting a high pressure pump, a-drive shaft for said barrel and said low pressure pump, said end plate having inlet and outlet ports therefor, said low pressure pump being adaptable for charging said high pressure pump, said end plate having a pump inlet and a pump outlet, a passageway arrangement from said pump inlet to said back plate, said back plate having inlet and outlet ports for said low pressure pump, said last passageway leading to said last inlet port, said passageway arrangement extending from the outlet port in said back plate to the inlet port in said end plate and the outlet port of said end plate extending to said pump outlet, said back, plate being rotatable through a 180 are for permitting reversal of the rotation of said low pressure and high pressure pumps, and a sealing means between said drive shaft for said pumps and said housing, said sealing means being located beyond said back plate.

10. In a two-stage hydraulic pressure pump, a housing, an end plate therefor, a barrel mounted for rotation in said housing, a cam, a low pressure pump and a back plate arranged in series in said housing, said barrel having a plurality of reciprocable pistons, said barrel, cam and pistons constituting a high pressure pump, said end plate having inlet and outlet ports therefor, said low pressure pump being adaptable for charging said high pressure pump, said end plate having a pump inlet and a pump outlet, a passageway arrangement from said pump inlet to said back plate, said back plate having inlet and outlet ports for said low pressure pump, said last passageway leading to said last inlet port, said passageway arrangement extending from the outlet port in said back plate to the inlet port in cal and plate and the outlet port of said end plate extending to said pump outlet, said back plate being rotatable through a 180 are for permitting reversal of the rotation of said low pressure and high pressure pumps.

11. In a two-stage hydraulic pressure pump, a housing, an end plate therefor, a barrel rotatably mounted in said housing, a cam, a low pressure pump and a back plate in said housing, said barrel having a plurality of reciprocabie pistons, said barrel. cam and pistons constituting a high pressure pump, said end plate having inlet and outlet ports therefor, said end plate having a pump inlet and a pump outlet, a passageway arrangement from said pump inlet to said back plate, said back plate having inlet and outlet ports for said low pressure pump, said last passageway leading to said last inlet port, said passageway arrangement extending from the outlet port in said back plate to the inlet port in said end plate and the outlet port of said end plate extending to said pump outlet, said back plate being rotatable through a half revolution for permitting reversal of the rotation of said low pressure and high pressure pumps.

12. In a two-stage hydraulic pressure pump, a housing, an end plate therefor, a barrel rotatably mounted in said housing, a cam, a low prim-sure pump and a back plate arranged in series in said housing, said barrel having a plurality of reciprocable pistons, said barrel, cam and pistons constituting a high pressure pump, said end plate having inlet and outlet ports therefor, said end plate having a pump inlet and a pump outlet, a passageway arrangement from said pump inlet to said back plate, said back plate having inlet and outlet ports for said low pressure pump, said last passageway leading to said last inlet port, said passageway arrangement extending from the outlet port in said back plate to the inlet port in said end plate and the outlet port of said end plate extending to said pump outlet.

13. In a pressure pump of the character disclosed, a housing, an end plate therefor, a barrel mounted for rotation in said housing, a cam, a low pressure pump and a back plate arranged in series in said housing, said barrel having a plurality of reciprocable pistons, said barrel, cam and pistons constituting a high pressure pump, said end plate having inlet and outlet ports therefor, said low pressure pump being adaptable for overcharging said high pressure pump, said end plate having a pump inlet and a pump outlet, a passageway arrangement from said pump inlet to said back plate, said back plate having inlet and outlet ports for said low pressure pump, said last passageway leading to said last inlet port, said passageway arrangement extending from the outlet port in said back plate to the inlet port in said end plate and the outlet port of said end plate extending to said pump outlet, said back plate and said cam being rotatable through for permitting reversal of the rotation of said low pressure and high pressure pumps, and said passageway arrangement including .hollow dowels extending radially into said housing and said back plate and communicating with the low pressure pump inlet and outlet ports thereof.

14. In a hydraulic pressure pump of two-stage character, a housing, a barrel driving shaft journaled therein, a barrel loosely mounted on said shaft, an end plate for said housing, said barrel having a plurality of cylinder bores, said barrel being engaged with said end plate under fiuid pressure against partially closed ends of said cylinder bores, pistons in said cylinder bores, a cam for sliding said pistons in one direction, a low pressure pump, said end plate having inlet and outlet ports for said cylinder bores, said low pressure pump charging said inlet port, said end plate having an intake and an outlet, said intake charging said low pressure pump and said outlet port charging said outlet of said end plate.

15. In a two-stage hydraulic pressure pump, a housing, a barrel rotatably mounted therein, an end plate for said housing, said barrel being engaged therewith and having a plurality of cylinder bores, pistons therein, a cam for sliding said pistons in one direction, a low pressure pump for charging said pistons with fluid, said end plate having inlet and outlet ports for said cylinder bores, said end plate having an intake and an outlet, said intake charging said low pressure pump and said outlet port charging said outlet of said end plate.

16. In a pump structure of the character disclosed, a cylindrical housing, an end plate there- 'on, a barrel against said end plate and having cylinder bores, pistons in said bores, a cam for sliding said pistons in one direction when said barrel is rotated, a sliding vane type pump in said housing next to said cam, a back plate thereadiacent, said back plate being adjustable through 180 for permitting reversal of the rotation of said piston and vane type pumps, said end plate having an inlet and an outlet, and a passageway arrangement from said inlet through said back plate to said vane pump, from enid rnne memo to said cylinder and piston pump, end from said eyiinder nnd pistonnump to said outlet oi said end plate. said magewny arrengement including dowels removably positioned in snid housing for retaining said back ninte ngninst rotation, said dowels being removniole to permit ndinstment oi the back plate and rnne pump. and one oi seid dowels so enacting with snid been pinte in such manner that the direetion of rotation can be determined thereby.

ii. In n pump structure oi the character diseinsed, n cylindrical! housing. an end plate thereon, n barrel egeinst enid end piete and having eyiinder ioores, nlstone in said bores. means for sliding snid pistons in one direction when said nor-rel is rotated, n sliding vane type pump in snid nonsinn, n back plate thereadiaeent, said been ninte being ndinstabie through 180 ior permitting reversal of the rotation of said piston nnd rnne tyne pumps, soid end plate having on m inlet and an outlet, and a passageway erranzed and piston pump to mid iiiltlet of sold end late.

WARD demos i=5 1 'ROBMT A. om.

n we mm The following reiermew are oi record in the die of this potent:

note

1i s? Aug. 28, 19% 2,015,423 mnndeid Sept. 24, M35 2,069,651 men Feb. 2, 1937 3,385,991) Huber Oct. 3, 19% 

